docs: def is_valid_complex_fault_mesh_spacing(self):
          """
          The `complex_fault_mesh_spacing` parameter can be None only if
          `rupture_mesh_spacing` is set. In that case it is identified with it.
          """
          rms = getattr(self, 'rupture_mesh_spacing', None)
          if rms and not getattr(self, 'complex_fault_mesh_spacing', None):
              self.complex_fault_mesh_spacing = self.rupture_mesh_spacing
          return True